The present invention relates generally to equipment and procedures employed in the performance of perfusion catherization procedures, and more particularly to a system for operating an angioplasty catheter in a pulsatile fashion in synchronization with a heartbeat.
The use of inflatable balloon catheters in the treatment of coronary conditions is widespread. Balloon catheters are commonly used to expand blockages in arteries. These blockages are a narrowing of an artery or other body vessel, and are referred to as stenoses. In angioplasty procedures, a guide catheter is introduced into the artery of the patient and guided through the artery until the distal tip of the catheter is at the desired location of the coronary artery near the stenosis. A dilation catheter having an inflatable balloon affixed to its distal end is introduced along the guide catheter and advanced into the patient until the balloon end is located at the stenosis. The balloon is subsequently inflated to expand it against the artery walls to expand, or dilate, the artery and compress the stenosis. This expansion can remove all of or a significant portion of the blockage when the balloon is inflated against the arterial walls for a preselected time or repeatedly inflated and deflated in a cycle to match that of the heartbeat of the patient.
Once the artery has been expanded, the balloon is deflated and it and the guide catheter are removed so that blood may again flow on its own through the artery. Restenosis is a condition where the arterial wall has been initially expanded by the balloon and the arterial blockage is open but the arterial wall contracts and adopts all of or part of its original, restricted state sometime after the balloon is deflated and removed. The rate of restenosis is believed to be lowered if longer inflation times are used during angioplasty balloon catheterization procedures.
The use of longer balloon inflation times may promote the occurrence of ischemia of the cardiac muscles. Ischemia is a local deficiency of oxygen in an area of the body caused by an obstruction in the blood vessels supplying blood to that area. To prevent ischemia, perfusion catheters are used in association with coronary angioplasty catheters. Perfusion catheters are catheters which permit the continuous flow of blood through the blockage during the inflation of the balloon in the artery.
An external pump is often used in perfusion angioplasty procedures in order to draw blood from the patient by way of an aspiration catheter and circulate it back through the perfusion catheter and past the distal end of the balloon. External blood pumps have been commonly used for regulating blood through coronary arteries during open-heart surgeries. These pumps may generally provide either a high or low pressure output. External perfusion pumps are well known, such as the one described in U.S. Pat. No. 5,066,282 issued Nov. 19, 1991. This patent is directed to a perfusion pump with a pulsation-damping mechanism that serves to smooth out pressure pulses of the pump during pumping. Other external pumps are known which use syringes as their primary components, such as that described in U.S. Pat. No. 3,447,479, issued Jun. 2, 1967 which discloses an arrangement of syringe pumps which perform alternating suction and pumping strokes. In the multiple syringe pump arrangement shown in this patent, four syringe pumps are powered by a motor-driven eccentric cam drive which utilizes return springs connected to the plungers of the syringe pumps in order to ensure a prompt return of the syringe pump plungers to their original, ready position within the syringes. The pumping cycle of such a mechanism is essentially "fixed" because of the curvature of the cam surfaces of the cam. It is not possible to adjust such a mechanical type system to mate its pumping action with a heartbeat.
The present invention is therefore directed to an angioplasty system with a control means for selectively controlling the inflation and deflation of an angioplasty balloon in synchronization with a patient's heartbeat in order to deflate the balloon while the heart is pumping and to inflate the balloon while the heart is at rest. The present invention therefore also dispenses with the need to utilize a perfusion catheter and its external perfusion pump.
In accordance with one aspect of the present invention, a heart monitor and a programmable controller are linked together so that the controller, in effect, "reads" the heart rate or pulse of the patient. The controller controls a bank, or a manifold, of valves that control the inflation and deflation of the angioplasty balloon using a biocompatible inflation media, such as helium or carbon dioxide. The valves are operatively connected to a pressurized source of inflation media as well as a vacuum source to provide for immediate inflation and deflation upon demand in response to a signal generated by the controller.
In another aspect of the present invention, a series of gas pressure regulators interconnect the pressurized inflation media source to a series of solenoid valves which are operatively connected to a programmable control means in order to regulate the pressure of the inflation fluid drawn from its source and used for balloon inflation purposes.
In yet another aspect of the present invention, the programmable controller has an adjustable control means with a timing delay means operatively associated therewith in order to adjust the frequency of the inflation and deflation cycles of the angioplasty balloon so that the balloon may be inflated and deflated in synchronization with the patient's heart so that angioplasty may be performed with minimal trauma and ischemia occurring. The timing delay means permits the programmable controller to synchronize the inflation of the balloon (and its deflation) not only to the heartbeat of the patient, but also in synchronization with a particular heartbeat, such as the fourth or sixth heartbeat, for example, in a chosen cycle.
Accordingly, it is a general object of the present invention to provide a pulsatile, synchronous inflation system for use in angioplasty which reduces trauma and ischemia.
Another object of the present invention is to provide a pulsatile angioplasty system wherein the balloon inflation pressure are adjustable and may be increased as required.
Still another object of the present invention is to provide an angioplasty inflation/deflation control system having a programmable controller which controls and regulates the inflation/deflation of an angioplasty balloon in synchronization with the heart rhythm of the patient, thereby permitting preselected longer or shorter periods of time of inflation during angioplasty and thereby reduces the trauma associated with angioplasty.
Yet another object of the present invention is to provide a synchronous, pulsatile angioplasty system having a control apparatus which synchronizes the inflation and deflation of an angioplasty balloon with the heartbeat of a patient and which controls the inflation and deflation times so that the angioplasty balloon may be inflated or deflated at every Nth heartbeat.
These and other objects, features and advantages of the present invention will be clearly understood through consideration of the following detailed description.